In the medical field, needle-less connectors are sometimes used in infusion or blood transfusion liquid passages in order to enable the connection and separation of syringes or transfusion bags. Such needle-less connectors have an elastic valve body provided at the tip end opening of a drug solution flow path formed in a housing as described in FIG. 1 of the specifications of U.S. Pat. No. 6,171,287 (Patent Document 1). The base end of the drug solution flow path can be connected to a catheter, where the connection between the catheter inserted into the blood vessel and base end of the drug solution flow path connects the drug solution flow path and the blood vessel.
The insertion from outside of the male luer into a slit which is formed in the elastic valve body so as to penetrate therethrough, opens the elastic valve body and connects the drug solution flow path and the male luer. In this state, medical liquid is made to flow into the needle-less connector from a syringe and the like connected to the male luer to administer the medical liquid to the patient. Once the administration of the medical liquid is completed, the male luer is extracted from the slit, which closes with the recovery of the elastic valve both to its original state. As a result, the tip end opening of the drug solution flow path is cut off by the elastic valve body, enabling the male luer to be separated from the drug solution flow path connected to the blood vessel and the like.
When extracting the male luer from the slit in a needle-less connector, blood may enter the catheter connected to the drug solution flow path from the blood vessel (back flow of blood), creating a risk of blood coagulation. This led to demand for a needle-less connector in which the back flow of blood upon extraction of the male luer from the slit could be prevented.
The needle-less connector as described in the above Patent Document 1 has a conventional structure in which the tip end opening of the drug solution flow path gradually widens towards the elastic valve body. However, in this structure, since the end surface of the drug solution flow path side at the elastic valve body is not supported, the central section of the elastic valve body undergoes elastic deformation inwards from the tip end opening of the drug solution flow path when inserting the male luer from outside. As a result, the extraction of the male luer causes an expansion in the volume of the drug solution flow path connected to the blood vessel which accompanies the recovery of the elastic valve body to its original state. This creates a suction force of blood to the drug solution flow path, increasing the risk of the back flow of blood.
Japanese Domestic Publication of International Patent Application No. JP-A-2009-544449 (Patent Document 2) proposes a structure in order to prevent such a back flow of blood which involves the embedding of a hard material along with the formation of an inside chamber in the partition or valve. In this structure, as described in Patent Document 2, the back flow of blood is prevented by an expansion of the volume of the inside chamber which accompanies the elastic deformation of the partition when inserting the tip end section of the male luer, which then causes a reduction in the volume of the inside chamber upon extraction of the tip end section.
However, even in the structure as described in Patent Document 2, although the inside chamber was extended with the insertion of the tip end section of the male luer into the partition or valve, the partition would deform so as to penetrate the inside chamber and a sufficient expansion of the inside chamber was difficult to achieve. Thus, it was difficult to demonstrate a sufficient effect of preventing the back flow of blood. In addition, manufacturing was made difficult due to the compound structure of the partition or valve with a hard material as well as its complex shape. There was also the problem that handling may be more difficult as a result of increased rigidity due to the restriction of the elastic deformation of the elastic body partition by the hard material as well as the difficulty of having sufficient durability to deal with the risk of cracking due to the concentration of deforming stress.